This invention relates to a device for the automatic adjustment of the movement and locking mechanism of an injection molding press for plastics, elastomers or the like.
Injection molding presses generally comprise a fixed plate and a movable plate each bearing, respectively, the two halves of a mold, a second fixed plate or bed connected to the movable mold bearing plate, and a mechanism for moving and locking the movable half mold against the fixed half mold. The moving and locking mechanism is often formed by a high force locking jack with a small range of movement which is connected to the bed, and a second movable plate connected to the movable half mold bearing plate by two articulated levers forming an elbow joint, the latter being controlled by a low force jack with a large range of movement. The movement of the movable half mold towards the fixed half mold is implemented by the elbow jointed levers, whereas the locking jack provides the pressurization of the two half molds during the injection and during the detaching of the two half molds after injection.
When changing the molds in such a press, the thickness of the molds generally varies and it is necessary to carry out adjustments of the movement of the locking jack so that, when the two half molds are brought together by the elbow jointed levers, there is only a small space remaining between the two half molds. This space should be sufficiently large for the straight alignment of the two levers to be correctly effected during the closing of the mold, but small enough to both minimize the range of movement of the locking jack and to prevent foreign objects from entering between the two half molds. These two conditions are necessary as, on the one hand, the levers should be aligned so that the force of the locking jack is correctly applied to the two half molds, and on the other hand, the movement of the locking jack should be as small as possible to allow it to be rapidly placed under pressure. Since the force created by this locking jack is considerable, if a foreign object were to be introduced between the two half molds it could cause destruction or deformation of the mold.
The adjustments due to the change in thickness of the molds are generally complex and therefore lengthy to carry out, and must be made each time the mold thickness is changed.